Bruce Tharp designed one or two of the 4* series and he mentioned that the rudder didn't have enough authority.

I am going to order the 4*40 kit and do some mods along the same lines you are. I am pretty sure by now that I'll chop off 2 rib bays on the wing and extend the tips some to look like a Smoothie. Same shape for the stabilizer/elevator. I'll make counterbalances for those too. I like how you widened the ailerons. I was thinking about that and saw where you did it. Good idea, it seems. The Smoothie canopy is almost identical to the 4*, but the Smoothie looks much nicer and has more style overall. I guess I'll not exend the ailerons to the tips to cut down on flutter possibilities at higher speeds.

I'm going to overpower the 4*40 with something along the lines of a Saito .82. Haven't decided yet. I have a .72 that may haul it around fast enough too.